<!DOCTYPE html>
<html>
<head>
  <style>
    #scroller {
      height: 2000px;
      width: 300px;
      background-color: blue;
    }
  </style>
</head>
<body>
  <div id="scroller"></div>
  <portal src="activate-predecessor.html"></portal>
  <script>
    document.body.addEventListener('touchstart', e => {
      var portal = document.querySelector('portal');
      portal.activate().then(() => {
        document.body.removeChild(portal);
      });
    }, {passive: false, once: true});
  </script>
</body>
</html>
